import com.fasterxml.jackson.databind.ObjectMapper;
import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

class Message{
    //属性必须要设置成public
    //如果设置成private就需要生成public的getter和setter
    public String from;
    public String to;
    public String message;

    @Override
    public String toString(){
        return "Message{"+
                "from='"+from+'\''+
                ",to='"+to+'\''+
                ",message='"+message+'\''+
                '}';
    }
}

@WebServlet("/message")
public class MessageServlet extends HttpServlet {
    private ObjectMapper objectMapper=new ObjectMapper();
    //private List<Message> messageList=new ArrayList<>();
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //通过这个方法来处理”获取所有留言消息“
        //需要返回一个json字符串数组，jackson已经处理好了格式
        List<Message> messageList=load();
        String respString=objectMapper.writeValueAsString(messageList);
        resp.setContentType("application/json;charset=utf8");
        resp.getWriter().write(respString);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //通过这个方法来处理”提交新消息“
        Message message=objectMapper.readValue(req.getInputStream(),Message.class);
        //messageList.add(message);
        save(message);
        System.out.println("消息提交成功！message="+message);

        //响应只是返回200报文，body为空，此时不需要额外处理，默认就是返回200
    }

    //向数据库存储记录
    private void save(Message message) {
        DataSource dataSource=new MysqlDataSource();
        ((MysqlDataSource)dataSource).setUrl("jdbc:mysql://127.0.0.1:3306/demo?characterEncoding=utf8&useSSL=false");
        ((MysqlDataSource)dataSource).setUser("root");
        ((MysqlDataSource)dataSource).setPassword("root");
        try {
            Connection connection = dataSource.getConnection();
            String sql="insert into message values(?,?,?)";
            PreparedStatement statement=connection.prepareStatement(sql);
            statement.setString(1,message.from);
            statement.setString(2,message.to);
            statement.setString(3,message.message);
            statement.executeUpdate();
            statement.close();
            connection.close();
        }catch(SQLException e){
            e.printStackTrace();
        }
    }
    //从数据库查询记录
    private List<Message> load() {
        List<Message> messageList=new ArrayList<>();

        DataSource dataSource=new MysqlDataSource();
        ((MysqlDataSource)dataSource).setUrl("jdbc:mysql://127.0.0.1:3306/demo?characterEncoding=utf8&useSSL=false");
        ((MysqlDataSource)dataSource).setUser("root");
        ((MysqlDataSource)dataSource).setPassword("root");
        try {
            Connection connection = dataSource.getConnection();
            String sql="select * from message";
            PreparedStatement statement=connection.prepareStatement(sql);
            ResultSet resultSet=statement.executeQuery();
            while (resultSet.next()){
                Message message=new Message();
                message.from=resultSet.getString("from");
                message.to=resultSet.getString("to");
                message.message=resultSet.getString("message");
                messageList.add(message);
            }
            resultSet.close();
            statement.close();
            connection.close();
        }catch(SQLException e){
            e.printStackTrace();
        }
        return messageList;
    }
}

